The present invention relates to an apparatus and method for manufacturing multi-component plastic molded parts.
Typically, in a first cycle of the manufacturing process of multi-component plastic molded parts, a preform is made from a first component in a first cavity. Subsequently, the second component is molded onto the preform in a second cavity. The individual components can be made of different thermoplastics and may have different colors. Certain components may also be provided with filler material. Instead of thermoplastic components, polyurethane (PUR) components can be provided. It is also known to manufacture multi-component plastic molded parts having a thermoplastic component and a PUR component.
German patent DE 196 50 854 discloses a method and an apparatus for manufacturing multi-component plastic molded parts using rotary table techniques. An injection-molded plastic part is hereby coated with at least one layer of a 2-component thermoset. Both components are successively molded in the same mold in a cycle-synchronous manner. A base plate is hereby used which carries two identical half-molds side-by-side. The base plate is supported for rotation about a horizontal and longitudinal machine axis. Female molds of an injection molding machine and a RIM apparatus are arranged opposite the half-molds. After the injecting molding machine injects thermoplastic material, the base plate is rotated by 180° about the horizontal and longitudinal machine axis. In the next cycle, a new thermoplastic part is molded and the thermoplastic part of the first cycle is coated with the 2-component thermoset.
The article “Hochwertige Premiumoberflächen aus Spritzgieβ- und Reaktionstechnik”, [High-Quality Premium Surfaces Made by Injection-Molding and Reaction Techniques], describes on pages 180-182 in the October 2004 edition of the magazine “Kunststoffe” [Plastics] another method for manufacturing multi-component plastic molded parts from a first thermoplastic component and a second PUR component. A station for injecting the thermoplastic material is provided on the fixed side of a clamping unit of a known injection molding machine. On the movable side, a mixing head of a RIM apparatus (RIM: Reaction Injection Molding) for the PUR component is docked to the half-mold that is arranged there. RIM apparatuses are known and essentially include conveying and metering devices for individual chemicals to be processed, such as polyol, polyisocyanate, and possible additives, such as dyes, foaming agents, etc. A sliding table for the fixed half-mold is provided at the fixed side of the clamping unit in order to move the fixed half-mold from the position “injection molding” to the position “PUR molding”, and vice versa. In the mold position “injection molding”, a carrier such as a carrier made of polyamide plastics is pre-molded. At the end of the cooling period, the mold opens and the sliding table moves to the position “PUR molding”. After the mold closes, the PUR molding skin is injected into the enlarged cavity via the mixing head that is connected with the RIM mixing and metering unit.
It is further known in the related art to produce multi-component plastic molded parts using so-called reversing plate techniques (Johnnaber/Michaeli, Handbuch Spritzgieβen, [Handbook Injection Molding] 2001, ISBN 3-446-15632-1, Picture 6.80 on page 508). A middle platen, often called a reversing plate, is hereby rotatably supported between two outer platens. After the preform is produced in the first parting plane, the middle platen transports the preform to the second parting plane. There, the second component is molded onto the preform.
WO 03/013824 discloses manufacturing of multi-component plastic molded parts from a thermoplastic carrier and a PUR molding skin using the reversing plate techniques. A machine frame movably supports two outer platens. A supporting frame is mounted on the machine bed between the two outer platens. In the machine bed, a middle platen is supported for rotation about a vertical rotation axis. The middle platen can be plate-shaped and receive two half-molds. Alternatively, the middle platen can be cube-shaped so as to receive four half-molds. A suitable drive-and-locking-assembly can move the outer platens towards and away from the middle platen and lock the platens. In order to produce a multi-component molded plastic part from a thermoplastic base component and a PUR molding skin, one of the outer platens can be coupled with an injection unit for the thermoplastic base component, and the other outer platen can be coupled with a RIM apparatus. Handling robots, such as a processing robot and a removal robot, can be provided to the side of the clamping unit. For example, the processing robot can treat the surface of the base component. In a first cycle, the base component is made of thermoplastic material and is injection-molded on the side of the injection unit. After the required cooling period, the clamping unit is opened and the just molded base component is surface-treated. The platen is rotated by 180°, and the half-molds are closed again. In the subsequent cycle, a new thermoplastic base component is molded on the side of the injection unit, whereas, on the opposite side, a PUR reaction mixture is injected into the mold via a mixing head and a PUR skin is formed on the surface of the base component.
Common to the prior art described above is the production of a preform in the one parting plane and molding of the second component onto the preform in the other parting plane while a new preform is produced in the first parting plane at the same time.
It would therefore be desirable and advantageous to provide a method and an apparatus to obviate prior art shortcomings and to increase productivity in producing multi-component molded plastic parts.